Journal article

Publication year: 2016

Pages: 102-109

Journal: Soil Biology and Biochemistry

Volume number: 100

ISSN: 0038-0717

Open access status: Green

DOI Link: https://doi.org/10.1016/j.soilbio.2016.06.002

Publisher: Elsevier

Abstract: 
Changes in soil N-cycling and retention processes in subtropical/tropical acidic forest ecosystems under anthropogenic N inputs are not well understood. We conducted a laboratory N-15 tracing study on an acid soil (pH values: 4.6 to 5.0) from a subtropical forest fertilized for more than 2.5 years at a rate of 0, 40, and 120 kg NH4Cl-N ha(-1) yr(-1), respectively. To get a better resolution of mechanistic changes in soil N cycling and retention processes under NHS additions, we used a conceptual N-15 tracing model to quantify process-specific and pool-specific N transformation rates in soils. Gross N mineralization rates decreased at high NH4+ additions, which were paralleled by a reduction in fungal biomass and mineralization of recalcitrant organic N. Gross NHS immobilization rates did not show a change with increasing NH4+ additions. Interestingly, soil NO3- production (heterotrophic, autotrophic, and gross nitrification) and retention (NO3- immobilization and dissimilatory nitrate reduction to ammonium) showed insensitivity to increasing additions of NH4+. The mechanisms behind the lack of response of heterotrophic nitrification were unclear, but possibly related to the absence of significant changes in soil C:N ratio and soil acidity under increased NH4+ additions. Because of the low autotrophic nitrification potential and the lack of NH4+ limitation to autotrophic nitrifiers, autotrophic nitrification was unresponsive to NH4+ additions. NO3- immobilization rates appeared to be controlled by the NO3- produced from heterotrophic nitrification, as indicated by the positive relationship between NO3- immobilization and heterotrophic nitrification (R-2 = 0.59, p = 0.015), thus showing a lack of a change under increased NH4+ additions. DNRA seemed to be inherently less responsive to environmental changes such as NH4+ deposition. Our work demonstrates that enhanced NH4+ deposition has a low potential to stimulate soil NO3- production and weaken soil retention of NO3- in this, and perhaps other subtropical/tropical acidic forest ecosystems. (C) 2016 Elsevier Ltd. All rights reserved.

Harvard Citation style: Gao, W., Kou, L., Yang, H., Zhang, J., Müller, C. and Li, S. (2016) Are nitrate production and retention processes in subtropical acidic forest soils responsive to ammonium deposition?, Soil Biology and Biochemistry, 100, pp. 102-109. https://doi.org/10.1016/j.soilbio.2016.06.002

APA Citation style: Gao, W., Kou, L., Yang, H., Zhang, J., Müller, C., & Li, S. (2016). Are nitrate production and retention processes in subtropical acidic forest soils responsive to ammonium deposition?. Soil Biology and Biochemistry. 100, 102-109. https://doi.org/10.1016/j.soilbio.2016.06.002